The Russian track-and-field federation says it has launched an investigation after dozens of athletes suddenly withdrew from a competition in Irkutsk following the arrival of drug testers.

The federation said in a statement on January 17 that it has asked the athletes to explain their reasons for withdrawing and "has started an internal investigation."

The Russian sports website Championat reported that 36 athletes withdrew from a Siberian indoor championship meet in Irkutsk last week, with some citing illness, after drug testers from Russia's anti-doping laboratory unexpectedly arrived at the event.

The federation said it had suggested that the anti-doping agency RUSADA pay closer attention to regional and junior competitions as it has found that "certain problems with doping are present in this segment of Russian track and field."

It's not the first time Russian athletes have been accused of dodging doping tests. The federation launched an investigation into five sudden withdrawals at a meet last year but hasn't reported any results from the probe.

Russian athletics federation Director Andrei Kruporushnikov said he "didn't expect" such mass withdrawals when the federation suggested that RUSADA look into second-tier races.

He told Russia's Sport Express newspaper on January 17 that RUSADA should closely scrutinize all the athletes who canceled their races.

While Kruporushnikov said lower-level sport in Russia has "serious problems" with doping, he contended that Russia's national team is "the cleanest and most checked in the world."

Russia's national athletics team has been banned from competing in international events since November 2015, when allegations of widespread doping in Russia first emerged. The team was also banned from the 2016 Summer Olympics in Rio de Janiero.